We're going to do an activity on the Phases of the Moon this afternoon, so
I'll skip most of the discussion for now.
In the same way that the Earth rotates an "extra" time for each complete
orbit of the Sun, so the Moon actually rotates once per orbit of the Earth --
even though the same side always faces us, which one might think to be no rotation.
One point that needs explanation is the difference in duration
between one rotation of the Moon, and one complete cycle of phases.
The extra amount the Moon rotates to complete a phase is equal to
the amount the Earth has rotated around the Sun to over the phase: